A multimillion-dollar proposal to transform a run-down Crown Street building into a cafe and rooftop bar has been given the green light.

Wollongong City Council has approved a development application for refurbishment on the building at 226-228 Crown Street which will include external facade works and internal fit-out.

The site, on the corner of Crown Street and Crown Lane, is the old Hillman Humber building which dates back to the 1930s.

As a homage to its previous use, the three-level business will be known as Humber - Kitchen Bar & Rooftop.

A fresh food kitchen open for breakfast and lunch will occupy the ground floor and the first floor and rooftop will feature bars.

The building, owned by GPT Group, was set to be demolished as part of the original mall expansion, however the company successfully lodged a modification to keep the block.

The premises would be leased and fitted out by a company called Opes Entertainment and managed by Hotel Illawarra licensee Dwayne Robinson, according to council documents.

The proposed ground floor cafe would seat 34 people, while the first floor would have cocktail bars and seating for 83. The rooftop terrace would seat 100 people in covered and uncovered areas with an outdoor cocktail station.

The bar would stay open until 1am seven nights a week, with the rooftop closing at midnight.

Humber has its own Facebook page and has already attracted strong interest with more than 3500 people liking the page.

"Humber is a venue like the Illawarra has never before seen," Humber's proponents said on the cafe/bar's official Facebook site.

"Designed in 2013-14 with a multimillion-dollar investment using award winning Sydney-based hospitality designers and state of the art technology and fit-out components - resulting in a unique experience to the region, Humber is sure to be a game changer in the marketplace ... a true point of difference."